The objective is the measurement of the contact angle of a variety of bacteria and particles and its correlation with their phagocytosis, as well as the study of the influence of specific antibody, aspecific immunoglobulins, complement and other additives, including detergents, antibiotics and other solutes, on these two phenomena. The study will also encompass the measurement of the contact angle of neutrophils and macrophages as well as of other cells, in order to elucidate the phagocytic capacity of the first two types of cells and to correlate these data with their interaction with other cells.